1. Field of the Invention
This invention relates to agricultural trailed equipment used in the application of liquid chemicals and more particularly to a plastic liquid chemical tank to increase the capacity of the applicator and, at the same time, maintain a short coupled low profile trailer for better tracking and visibility.
2. Description of the Prior Art
Agricultural trailed chemical application equipment generally consists of a rolling framework that supports a reservoir to carry liquid chemical product. The product contained in the reservoir is delivered to various locations along a boom mounted to the framework for accurately dispensing at a desired latitudinal distance from the centerline of the main trailer towing vehicle or tractor. The trailer is attached to the tractor through a load bearing pivot point at the rear of the tractor which allows the tractor-trailer combination to articulate for steering purposes.
The economy of chemical application is continuously improving by increasing the latitudinal distance, swath width, of the application equipment in an effort reduce the number of passes required for a given area of land. In addition to increasing the boom lengths, larger liquid chemical tank capacities are also desired to reduce the number of reloading operations that are required. As agricultural semi-trailed chemical application equipment has grown larger in size the accepted practice of increasing the liquid chemical tank's capacity is to retain a generally rectangular or elliptical profile and lengthen and/or raise the overall height of the tank. The lateral dimension of the tank is usually limited by Department of Transportation (D.O.T.) regulations which do not allow shipping or hauling of equipment more than twelve feet (3.66 meters) in overall width without special road permits. Lengthening the liquid chemical tank also in effect lengthens the trailer, thereby moving the rear mounted boom and axle arrangement back away from the towing vehicle. The axle assembly must move proportionally with the lengthened tank in order to maintain a proper balance of the trailer unit to the hitch point, thereby minimizing or eliminating the reverse gravitational hitch loads.
Increasing the distance between the tractor hitch pin and the trailer's axle, however, reduces the trailer's ability to effectively follow in the same wheel track as the towing vehicle. This off-tracking is a common characteristic of fixed axle semi-trailed equipment whenever the refraction angle at the hitch point deviates from an aligned position such as when turning or steering corrections are necessary. Wheel off-tracking is also exaggerated on trailing equipment when traversing a side slope where the gravitational force tends to pull or slide the trailer down the slope causing the trailer to yaw from an optimal path in which the center line of the trailer is aligned simultaneously with the centerline of the towing vehicle. Whether the result of side slopes or necessary navigating functions, whenever the trailer's wheel path deviates from the tractors wheel track, there is a substantial risk of increased crop damage and loss of overall yield.
Increasing the overall height of the tank to obtain more tank capacity greatly raises the center of gravity and obstructs rear view. Raising the center of gravity causes the trailer assembly to become less stable and more susceptible to roll over.
Typically a plastic liquid chemical tank is secured to the trailer framework by means of nylon straps or a formed steel members that circumnavigate the tank and bolt to the trailer frame work. As well as securing the tank to the trailer's framework the formed steel members, or “hoops”, can also provide structural integrity to the plastic tank and help maintain the original rectangular or elliptical profile.